Electrical control systems

ABSTRACT

An electrical control system, particularly for a choke cable on a vehicle, includes a pair of electromagnets, each of which when energized moves the choke cable back from its operative position to its inoperative position. The first electromagnet is energized when the engine temperature rises to a predetermined value, moves the choke cable back, and brings the second electromagnet into the circuit in series with a resistor which determines when the second electromagnet is energized. When the second electromagnet is energized, it moves the choke cable back further, and brings the first electromagnet back into the circuit in series with a resistor which determines the engine temperature at which the first electromagnet is energized again. This sequence continues until the choke cable returns to its rest position. Other parameters can be controlled in a similar way.

United States Patent Holt 1 51 Mar. 28, 1972 154] ELECTRICAL CONTROLSYSTEMS 3,586,869 6/1971 Kompelien ..307/117 x [72] Inventor: WilliamDavid Holt, Colne, England Primary Examiner Roben K schaefer [73]Assignee: Joseph Lucas (Industries) Limited, Bir-AS81318"!Examiner-William ith mingham, England Anomey-l-lolman & Stern[22] Filed: Jan. 6, 1971 57 ABSTRACT PP 1041234 An electrical controlsystem, particularly for a choke cable on a vehicle, includes a pair ofelectromagnets, each of which when energized moves the choke cable backfrom its opera- [30] Foreign Application Priority Data tive position toits inoperative position. The first electromag- Jan. 17, 1970 GreatBritain ..2,369/70 net is energized when the engine temperature rises toa predetermined value, moves the choke cable back, and brings [52] US.Cl ..307/117, 123/32 EA, 317/ 148.5 B, h on lcctromagnct into the ciruit in series with a re- 317/155 5 sistor which determines when thesecond electromagnet is [5i] lnt.Cl. ..H0lh 47/26 energized when secondelectmmagnet is energized, it [58] Field of Search ..307/117; 317/198.5B, 155.5; moves the choke cable back further, and brings the first elec-123 /32 EA, 119 F tromagnet back into the circuit in series with aresistor which determines the engine temperature at which the firstelec- [56] References Cited tromagnet is energized again. This sequencecontinues until the choke cable returns to its rest position. Otherparameters UNITED STATES PATENTS can be controlled in a similar way.

3,533,381 10/1970 Schmid ..l23/32 EA 1 Claim, 1 Drawing FigureELECTRICAL CONTROL SYSTEMS This invention relates to electrical controlsystems for operating a pair of electromagnets alternately in responseto variations of a parameter.

A system according to the invention comprises in combination a pair ofsupply lines, a resistor connected across the supply lines, the resistorhaving a value which varies with said parameter, a first electromagnethaving one end connected to one of said supply lines and its other endconnected to the movable contact of a multiposition switch having aplurality of operative fixed contacts, a plurality of preset resistorsconnecting said operative contacts to the other supply line, a secondelectromagnet having one end connected to one of the supply lines andits other end connected to the movable contact of a second multipositionswitch having a plurality of operative fixed contacts, a plurality ofpreset resistors connecting .the operative fixed contacts of the secondswitch to the other supply line, the arrangement of the electromagnetsand switches being such that at any given time the resistor having avalue dependent on the parameter is connected between the lines inparallel with a series combination including one of the preset resistorsand one of the electromagnets, current flow through a preset resistor toan electromagnet being insufficient to energize the electromagnet, andthe system further including means for energizing one of theelectromagnets whenever the value of the resistor associated with thevarying parameter reaches a value determined by the preset resistor inuse at that moment, each of said switches having a plurality ofnonoperative fixed contacts intermediate the operative fixed contacts,and the arrangement being such that when either electromagnet isenergized, both switches are moved onto their next fixed contact, thecircuit to the energized electromagnet is broken, and the switchassociated with the other electromagnet moves onto an operative fixedcontact to connect a further preset resistor in series with the saidother electromagnet between the supply lines.

The accompanying drawing is a circuit diagram illustrating one exampleof the invention.

Referring to the drawing, the battery of a road vehicle has its negativeterminal connected to an earth supply line 12, and its positive terminalconnected through a switch 13 which is closed only when the voltageregulator of the vehicle is operating, and resistors 11, 14 in serieswith the switch 13, to a supply line 15, the voltage between the lines15 and 12 being stabilized by a Zener diode 16, connected between thejunction of the resistors 11, 14 and the line 12. The arrangementfurther includes a first rotary or other multiposition switch having amovable contact 17 which is movable in use sequentially over fixedcontacts 22, 21, 20, l9, 18 in that order. The contacts 18, 20, 22 areoperative fixed contacts, the contacts 18 and being connectedrespectively to one. end of eachof two preset resistors 23, 24 the otherends of these resistors being connected through a diode 51 to the line15. The contact 22 is connected to a supply line 25 connected to thepositive battery terminal through the switch 13 and the contacts 19 and21 are nonoperative fixed contacts. The movable contact 17 is connectedto the line 12 through an electromagnet 28.

A second rotary or other multiposition switch is also pro: vided havinga movable contact 29 which is movable in use sequentially over fixedcontacts 34, 33, 32, 31, 30 in that order. The contacts 30, 32 and 34are nonoperative, but the contacts 31 and 33 are operative and areconnected through resistors 35 and 36 respectively to the cathode of thediode 51. The movable contact 29 is connected to the line 12 through asecond electromagnet 37.

The line 15 is connected through a resistor 26 to the base of anNPN-transistor 38, having its base connected through a variable resistor39 and a thermistor S2 in parallel to the line 12, its emitter connectedto the line 12 and its collector connected through a resistor 41 to theline 25. The collector of the transistors 38 is further connectedthrough a diode 42 to the gate of a thyristor 43, the anode of which isconnected to the line 25, the gate of which is connected through aresistor 53 to the line 12, and the cathode of which is connectedthrough diodes 44, 45, 46 and 47 respectively to the contacts 18, 20, 31and 33. Finally, a resistor 27 having a value determined by somevariable parameter is'connected across the lines 15, 12.

Although of course the arrangement can be used for a variety ofpurposes, the specific example described is for use in a vehicle havingan automatic choke control. The choke is moved to its operative positionmanually, but is returned to its nonoperative position with increasingengine temperature by the electromagnets 28 and 37, which require to beenergized in turn. For the purposes of the present description, all thatis required to be known is that the electromagnets 28 and 37 are to beenergized alternately, and that the resistor 27 is sensitive to enginetemperature, and has a sharply decreasing resistance with increasingtemperature. Typically a resistor is used having a resistance of 2,300ohms at minus 5 C falling to ohms at 55 C.

In use, when the choke knob is pulled out, the contacts 29 and 17 aremoved into engagement with the contacts 34 and 22 respectively. When theengine is started, then once the speed of the generator reaches apredetermined value, the voltage regulator operates and closes thecontact 13. The electromagnet 28 is now energized by way of the contacts22, 17,

energization of the electromagnet 28 serving to move thev choke cableback towards its inoperative position, but in addition moving thecontact 17 onto the contact 21 and the contact 29 onto the contact 33.The circuit to the electromagnet 28 is now broken, and the electromagnet37 is not energized, because the current flowing in the electromagnet 37by way of the resistors 11, 14, the diode 51 and the resistor 36 isinsufficient to energize the electromagnet 37. However, when thetemperature sensed by the resistor 27 rises to a predetermined value,then the value of the resistor 27 will fall to a level at which thetransistor 38 turns off, and current flows by way of the resistor 41 anddiode 42 to turn on the thyristor 43. Current can now flow through thediode 47 to energize the electromagnet 37, which moves the choke cablefurther back towards its inoperative position, and in addition moves thecontact 29 onto the contact 32 and the contact 17 onto the contact 20.The circuit to the electromagnet 37 is now broken, and the electromagnet28 is not energized because current is flowing to it only through thepaths 11', 14, 51 and 24. At this stage the thyristor 43 is again off,because its circuit was broken upon movement of the contact 29 from thecontact 33.

When the engine temperature rises further, the thyristor 43 is turned onagain and the electromagnet 28 is energized by way of the diode 45. Thecontacts 17 and 29 now step onto the contacts 19 and 35 respectively,and the sequence continues with the electromagnet 37 being energized byway of the diode 46 when the engine temperature has risen further,whereupon the contacts 17 and 29 step to the position shown. Finally,the electromagnet 28 is energized by way of the diode 44, at which pointthe choke cable is in its inoperative position and the contacts 17 and29 are stepped to their final off position.

It will be appreciated that the engine temperatures at which the chokecable is moved back step by step are determined by suitable choice ofthe resistors 23, 24 35 and 36.

The thermistor S2 caters for changes in ambient temperature, and it willbe appreciated that the overall effect of the circuit is to return thechoke gradually to its inoperative position as the temperature of theengine increases.

It will be appreciated that the circuit can be used to control otherarrangements in response to variation of a parameter.

Having thus described my invention what I claim as new and desire tosecure by Letters patent is:

1. An electrical control system for operating a pair of electromagnetsalternately in response to variations of a parameter, comprising incombination a pair of supply lines, a resistor connected across thesupply lines, the resistor having a value which varies with saidparameter, a first electromagnet having one end connected to one of saidsupply lines and its other end connected to the movable contact of amultiposition switch having a plurality of operative fixed contacts, aplurality of preset resistors connecting said operative contacts to theother supply line, a second electromagnet having one end connected toone of the supply lines and its other end connected to the movablecontact of a second multiposition switch having a plurality of operativefixed contacts, a plurality of preset resistors connecting the operativefixed contacts of the second switch to the other supply line, thearrangement of the electromagnets and switches being such that at anygiven time the resistor having a value dependent on the parameter isconnected between the lines in parallel with a series combinationincluding one of the preset resistors and one of the electromagnets,current flow through a preset resistor to an electromagnet, beinginsufiicient to energize the electromagnet, and the system furtherincluding means for energizing one of the electromagnets whenever thevalue of the resistor associated with the varying parameter reaches avalue determined by the preset resistor in use at that moment, each ofsaid switches having a plurality of nonoperative fixed contactsintermediate the operative fixed contacts, and the arrangement beingsuch that when either electromagnet is energized, both switches aremoved onto their next fixed contact, the circuit to the energizedelectromagnet is broken, and the switch associated with the otherelectromagnet moves onto an operative fixed contact to connect a furtherpreset resistor in series with the said other electromagnet between thesupply lines.

1. An electrical control system for operating a pair of electromagnetsalternately in response to variations of a parameter, comprising incombination a pair of supply lines, a resistor connected across thesupply lines, the resistor having a value which varies with saidparameter, a first electromagnet having one end connected to one of saidsupply lines and its other end connected to the movable contact of amultiposition switch having a plurality of operative fixed contacts, aplurality of preset resistors connecting said operative contacts to theother supply line, a second electromagnet having one end connected toone of the supply lines and its other end connected to the movablecontact of a second multiposition switch having a plurality of operativefixed contacts, a plurality of preset resistors connecting the operativefixed contacts of the second switch to the other supply line, thearrangement of the electromagnets and switches being such that at anygiven time the resistor having a value dependent on the parameter isconnected between the lines in parallel with a series combinationincluding one of the preset resistors and one of the electromagnets,current flow through a preset resistor to an electromagnet, beinginsufficient to energize the electromagnet, and the system furtherincluding means for energizing one of the electromagnets whenever thevalue of the resistor associated with the varying parameter reaches avalue determined by the preset resistor in use at that moment, each ofsaid switches having a plurality of nonoperative fixed contactsintermediate the operative fixed contacts, and the arrangement beingsuch that when either electromagnet is energized, both switches aremoved onto their next fixed contact, the circuit to the energizedelectromagnet is broken, and the switch associated with the otherelectromagnet moves onto an operative fixed contact to connect a furtherpreset resistor in series with the said other electromagnet between thesupply lines.